Question

The order in which the atomic radius increases is as follows

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

The general trend is that the atomic radius increases from boron to thalium. Only exception is that gallium is lower than aluminium. The smaller value of gallium in comparison to aluminium is due to the fact that the d-electrons do not screen the nuclear charge in an effective manner leading to a decrease in atomic radius. Thus
$B<Ga<Al<In<Tl.$